21-100244-SU-Right of Way Improvement Modification Request-7-6-2021�I
LARSON
AND ASSOCIATES
dmapi,4, eagutee#16 &
W W W.RRLARSON.COM
July 2, 2021
City of Federal Way
RE: File #21-100244-00-SU; Technical Letter— Right of Way Improvement Modification Request
South Campus Estates Preliminary Plat
To: Kerry Murdock,
1. State Development Standard or City Code being changed:
Current city development standards do not allow for pervious asphalt pavement to be
located within the right of way due to maintenance concerns and possible shorter
lifecycles of these types of pavements. We are requesting that in lieu of a pervious
asphalt pathway proposal we be allowed to propose "ballasted" concrete sidewalk
along 366th frontage improvements to maintain the reservoir rock course below the
impervious concrete sidewalk surface but adhere to the city's requirement for
impervious surfaces within the city's right of way.
2. State why this is being requested.
We are requesting to allow implementation of this "ballasted" concrete sidewalk along
366th in lieu of the city's standard impervious concrete sidewalk. This request is to allow
the reservoir rock base course to remain below the impervious sidewalk surface and
continue providing stormwater "storage" within the voids of the rock and hydraulically
"linked" stormwater storage in concert with the proposed bioretention cell system
achieving flow control compliance for this project with ultimate infiltration of
stormwater to and through native subgrade below the sidewalk and bioretention cell
systems.
We feel that allowance to utilize this "hybrid" concrete sidewalk and storm system will
benefit both parties allowing the property owner and developer the ability to meet
project stormwater flow control requirements within the right of way to address
required project frontage improvements while ensuring the city's maintenance division
9027 Pacific Avenue, Suite 4, Tacoma WA 98444 Office (253) 474-3404 Fax (253) 473-7358
will not have to take over something that they are not prepared to maintain and with
concerns on lifecycle of pervious pavement hard surfaces.
3. List reports, supporting documents and attachments accompanying this request:
- Exhibit map describing area of proposed "ballasted" Concrete sidewalk
- City of Tacoma adopted standard detail for "Ballasted" concrete sidewalk
Please feel free to contact me at 253-474-3404 to discuss this Improvement Modification Request
described above.
Sincerely,
Grant J. Middleton, PE
Larson & Associates, Inc.
M[n
/761
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